This invention relates to a process for cleaning soiled materials, the wastewaters from the process being chemically, mechanically and biologically treated and then returned to the process.
The industrial cleaning of soiled materials is normally carried out in washing machines using a detergent-containing aqueous liquor. After the actual washing process, the washed material is repeatedly rinsed with water and then dried and further processed. In this process, the disposal of the wastewater accumulating, which is polluted with detergent residues and other ingredients, represents a considerable cost factor. In the washing of feather or downs or in the washing of raw hide for leather manufacture, the wastewater is polluted, for example, with large amounts of emulsified fat. In the washing of dyed cotton fabrics, for example in mechanical stone-wash washing with pumice stones or in the washing of blue jeans, the wastewater contains dissolved and/or dispersed dyes and fiber residues.
In view of stricter anti-pollution legislation, the untreated wastewater is no longer allowed to leave the process so that treatment of the wastewater is unavoidable. The high consumption of freshwater for the treatment process, especially in countries and regions with limited water resources, is also a considerable cost factor.
Accordingly, there is a need for a cleaning process for soiled materials which would involve minimal water consumption and hence could be operated less expensively than known processes and which, at the same time, would lead to reduced environmental pollution by wastewater.